Neurotological Long-Term Follow-up in Minamata Disease in Niigata, Japan

To determine the long-term influence of organic mercurial intoxication on audioaogical and equilibrium findings, we followed up 36 patients neurotologically during 1980-1987 and 1991-2000 at Kido Hospital in Niigata. Typical findings were as follows : 1. In pure-tone audiometry, 24 of 72 ears (33%) showed slight hearing deterioration and 3 (4%) showed improvement. 2. Spontaneous nystagmus had disappeared in 5 patients (14%), but appeared in new 13 patients (36%). Positional nystagmus did not improve in any patient, and deteriorated in 11 (31%).